Coal mine roof bolts are used in vast numbers in the mining industry to support or shore the roof of a coal mine. The bolts have a square-shaped head on one end thereof and a stem or shank 6 feet or more in length which is inserted in a hole drilled in the coal mine roof. An annular plate or disc is slidably positioned on the shank of the bolt next to the head and the shank is retained in the hole in the roof by an expansible mechanical means carried by the bolt by a resin-type adhesive or grout, or by a resin-assisted, expansible mechanical means.
Most of such overhead support bolts are placed or positioned in the roof in accordance with a roof support control plan which must be originated by each coal mine operator in accordance with applicable governmental safety laws and regulations and subsequently approved by the government. The bolts must be placed a certain distance apart or in a pattern to adequately support the roof, and the distance between the bolts will vary depending on the condition of the roof and the strata above.
Bolts in an approved roof control plan or pattern cannot be used to support heavy loads or impact loads unless the bolts are held in the roof by resin-type adhesives or grout and are fully grouted if the bolts are mechanically anchored in the roof or are resin-assisted, only light loads such as communication cables or the like can be carried by or suspended from the heads of the bolts. If such light loads are carried by the bolts, some of the plates under the heads of the bolts are structured to include a tang or other configurations which can be used to attach such loads to the plate.
If it is desired to support light or moderate loads from the roof, roof anchors or small bolts other than roof support bolts can be employed, the most common being a hollow, cylindrical mechanical-type anchor 8 inches in length with a longitudinally-split periphery and which includes a frustoconical shaped nut on the upper inner end thereof adapted to receive a long threaded stud. When the stud is turned in the nut, the upper end of the cylindrical anchor is expanded in the hole in the roof in which it is inserted and the anchor is rigidly held in the hole. A load support is then threadedly attached to the free or opposite end of the stud for supporting a load from the roof. This type of anchor requires the drilling of a separate hole in the roof for each anchor and the drilling of the hole and the installation of the anchor is time consuming and expensive.
U.S. Pat. No. 4,958,796 was issued to the applicant on Sep. 25, 1990. The references cited against this patent showed several overhead supports for carrying a load including overhead supports for suspending or hanging a load from a coal mine roof. These references all used ceiling anchors or small bolts to support light or moderate loads instead of suspending or hanging a load from the head of a coal mine roof bolt. The couplings disclosed by the references also differed substantially in concept and structure from that utilized in the applicant's device.
For supporting heavy and moderate loads from the roof, it has been common practice for years to insert a separate roof bolt in the roof outside of the addition to the bolts in a roof control pattern. Such a separate roof bolt with any means for holding the bolt in a hole in the roof can be employed for supporting heavy or moderate loads, provided the condition of the roof will safely support the bolt and the load carried thereby.
It has also been common practice for years in the case of such bolts to use a length of angle iron with a separate roof bolt to suspend a load from the head of the bolt. The length of angle iron is provided with a hole in each strip or side thereof. One hole receives the shank of the roof bolt and the side of the angle iron having that hole therein is held against the roof by the head of the bolt when installed and functions as the circular plate normally carried under the head of the bolt. The hole in the other side of the angle iron can then be used to hold or receive a chain or any other type of load support whereby a heavy or moderate toad can be suspended from the head of the roof bolt. Using a separate bolt and the angle iron can be successfully employed to support such loads but this type or arrangement obviously requires the drilling of a separate hole in the roof and the installation of the bolt and angle iron, all of which again is very expensive and time consuming.
The use of a separate roof bolt for suspending a load from the roof could be eliminated in many instances if the existing roof bolts or the bolts that form part of a roof control plan and are fully resin grouted could be utilized to carry suspended or hanging loads. The present invention provides a device for so utilizing such roof bolts whereby a load can be suspended or hung from the head of a roof bolt forming part of an approved roof control plan.
U.S. Pat. No. 4,958,796 issued to the applicant on Sep. 25, 1990, also covers such a device although it differs substantially in structure from the coupling and load support of the present invention and is specifically structured to suspend or hang very heavy loads from the head of a coal mine roof bolt, loads ranging from 1000 lbs. to several tons.
The patented device includes a coupling which is made of heavy tool steel, which is circular in cross section and which has a much greater wall thickness so that it can be employed to carry the heavy loads. The patented device is rigidly attached to the head of a roof bolt by a plurality of bolts larger in size than those used in the applicant's device and are more expensive than the bolts utilized in the applicant's device, The patented device is vastly more expensive because of the use of tool steel and fabricating the coupling thereof is much more difficult and expensive, especially in tapping the threaded apertures that carry the bolts for attaching the coupling to the head of a roof bolt.
The coupling employed in the instant invention differs radically in structure from the patented device, is much lighter in weight, utilizes cheaper materials and components, can be inexpensively fabricated, and can be sold at a fraction of the cost of the patented device. The coupling of the present invention was designed and constructed to support light and moderate loads or loads up to 800 lbs., although the coupling can support, if need be, far greater loads from the head of a roof bolt, and under such greater loads the coupling will not slip or fall off of the head of the roof bolt, as will be discussed more in detail hereinafter.
The coupling of the present invention is comprised of a thin-walled, hollow, open-ended, substantially square-shaped housing which is dimensioned so that the open upper end thereof can be slidably received on the substantially square-shaped head of a roof bolt. The housing is rigidly connected to the head of the roof bolt by one or more bolts, preferably four, and the lower portion of the housing carries a threaded nut or the like, or is reduced in dimensions and is internally threaded, whereby a threaded stud can be employed to connect a load support to the housing so that a load can be suspended or hung from the head of the roof bolt.